Abstract: A calculation method for traffic capacity at intersections is a basic condition of urban congestion control. In view of the mixed release of traffic flow at urban road intersections, first of all, combined with the characteristics of traffic flow in all directions, it was clear that the traffic flow had the basic attributes of mixed release between signal control and nonsignal control. Secondly, the law of the conflict of traffic entities was applied and the concept of the complex coefficient of traffic conflicts and its traffic capacity reduction method were proposed under the mixed release of traffic flow. And the traditional traffic capacity theory was analyzed by analogy to obtain the traffic capacity calculation method of straight and rightturning directions. Thirdly, referring to the theory of crossing gap, the compensation benefit of left turn vehicles was introduced, and the capacity calculation method of left turn direction was obtained. Furtherly, a basic traffic capacity calculation model for common lane layouts was established. Finally, VISSIM was applied to obtain data and calibrate the reduction coefficient, so as to build a comprehensive calculation model for the capacity of the mixed release of traffic flow at intersections. The verification indicates that the calculated traffic capacity of the proposed model is basically consistent with the actual traffic capacity, with an average error of 4.9%, which better reflects the actual situation of the mixed release of traffic flow at intersections in China.

Key words: traffic and transportation engineering, traffic capacity, traffic flow, mixed release, traffic conflict

摘要： 交叉口通行能力计算方法是城市治堵的基础条件，针对城市道路交叉口合放交通流，首先结合其各方向交通流特性，明确了其具有介于信控与非信控间的合放基本属性；其次应用交通实体冲突规律，提出了合放下交通冲突复杂系数概念及其通行能力折减方法，并通过类比分析传统通行能力原理，得到直行、右转方向的通行能力计算方法；借鉴可穿越间隙理论，引入左转车补偿效益，得到左转方向的通行能力计算方法；并进一步建立常见车道布局的基本通行能力计算模型。最后，应用VISSIM获取数据并标定折减系数，从而构建了合放交叉口通行能力综合计算模型。验证表明:模型测算通行能力与实际通行能力基本一致，平均误差为4.9%，较好反映了我国合放交叉口的实际状况。

关键词: 交通运输工程, 通行能力, 交通流, 混合放行, 交通冲突